1. Field of the Invention
The present invention relates to a device for dosing and/or mixing highly viscous and non-flowable materials, more especially pigment pastes.
2. Discussion of the Background
The device is used in continuously operating and closed systems, more especially for dosing highly viscous and non-flowable materials in an extruder.
In a continuously operating and closed system the material can be supplied, for example, by means of an SRB-83076 Bxc3xchler pump whereby the pasty mass must be pressed into the pump from a hopper since it is barely drawn in by the pump itself. This can be accomplished by means of a pusher or a feed screw. It has been found that sticky non-flowing pastes adhere to the hopper and the feed components (feed screws, pushers). The adhered paste can only be loosened by scraping the components. In accordance with the principle of the invention all components in contact with product should mutually scrape each other and simultaneously press the material into the pump. For pasts which only acquire a pumpable consistency by shearing, such as pigment press cake for example, the material should be sheared by the scraping components. At the present state of the art several devices are known for dosing, or filling or discharging material.
German Patent Specification No. 1 180 321 discloses a silo with a discharging device having a rotatable bottom surface with driving vanes so that a considerable fraction of the fuel supply in the silo is rotated. The discharging device is a screw which is located directly above the contact surface and conveys the material from the center of the bottom radially towards a conveyor system positioned outside the silo.
Austrian Patent Specification No. 217959 describes a device for discharging masses from a silo and similar structures. In a cylindrical container with its bottom sloping towards the middle there is provided a drain hole. A radially configured screw rotates around the center, of the container and thereby sweeps the entire bottom of the container. In addition to the circling movement the screw spiral also executes a turning movement about its own longitudinal axis.
German Patent Specification DE 3304026 A1 discloses a silo with a discharging device which is provided with a screw which rotates such that the silo material is conveyed towards a feeder. When used as a distributing device the screw is driven in the opposite direction. In contrast to this, at the upper end of a conveyor shaft there-is provided another screw conveyor which can swing vertically towards the conveyor shaft and can rotate therein.
The problem for the present invention is to provide constant dosing of highly viscous and non-flowable materials such as pigment concentrates of all types (pigment press cake, offset pastes, offset concentrates, flush pastes), Aerosil pastes, die-stamping paints, all types of putty, gel pastes, gelled binders and so on. The device developed should avoid all the afore-mentioned disadvantages (adhesion of lumps, possible bridge formation).
The problem according to the invention is solved with the characteristics of the present invention. The invention starts from the afore-mentioned hopper which is used as a dosing device, as the latest technological development.
The problem is solved by the fact that a double screw is provided inside the hopper and the hopper turns about its own vertical axis. The screw replaces the currently used pusher or scraper which is usually positioned on the inner wall of the hopper. The screws brush each other and continuously brush the hopper wall. By means of the turning movement of the hopper, the product is continuously brushed away from the entire hopper wall.
Other advantageous embodiments of the invention are protected with the supplementary claims and result from these claims themselves or from combinations thereof.
It is advantageous for the distance between the inner wall of the hopper and the double screw to be in the range 0-3 cm.
It is advisable for the double screw to run along the hopper wall into a product outlet aperture at the lower end of the hopper.
It is advantageous for the screws of the double screw to be driven in the same direction or in opposite directions.
It is advantageous for the double screw to be driven in the same direction or in the opposite direction to the hopper.
It is advisable for the conveying capacity of the double screw to be higher than the conveying capacity of the pump.
It is advantageous that the screws beneath the hopper should be run through a housing to the pump.
It is advisable that the rotation rates of the screw should be in the range 20-100 rpm and those of the hopper should be in the range 1-5/min.